An electric motor is a machine that converts electric energy into mechanical energy. In an electric vehicle, the electric motor propels it by use of the electrical energy stored in a battery.
An IC engine vehicle uses the combustion process to generate the mechanical energy from the chemical energy. The combustion emits environmental polluting gases from the fossil fuels.
Electric motors does not emit gases and they are less noisy compared to the IC engine.
The convenience of speed control, robustness, efficiency, size, life, etc. decide which motor should be used in an electric vehicle. The evolution of power electronics controllers made speed control of electric machines easier.
Regenerative braking also becomes simple with power electronics controllers.
Following are the different types of traction motors commonly used in electric vehicles.
DC Machines in Electric Vehicles
Direct current motors are the traction motors that have been using for a long in an electric vehicle.
Easy speed control and speed-torque characteristics suitable for automobiles brought DC series motor to the upper edge in the list of motors used in the vehicle.
Speed torque characteristic of the series motor is much suitable for electric traction as its initial torque requirement is high and series motor can meet it.
Regenerative braking is difficult in DC series motor, and that is a disadvantage.
Electric trains used DC series motors for a long. Speed control of AC motors using power electronics converters helps them to be popular in an electric train.
DC shunt motors are another member of the group of electric vehicle motors. Permanent magnet DC shunt motors have succeeded in an electric scooter with its simple speed control and regeneration capability.
AC Motors in electric vehicles
Alternate Current motors become popular in the automotive industry since the development of power electronics. Speed control of AC motor becomes less complex with power electronics controllers.
AC induction motors are less expensive and low maintenance motor. But their speed-torque characteristic is not that suitable for an electric vehicle. Advancement of power electronics and variable frequency drives made it possible to use induction motors in electric vehicles.
Speed control becomes less complex in induction motors. Tesla Model S uses 3 phase 4 pole AC induction motor in its power train.
Synchronous motors also came into the picture of electric vehicle motors when power electronics get developed. Permanent Magnet Synchronous Machines (PMSM) are being used in Hybrid, Plug-in Hybrid, and Battery Electric Vehicles. They have advantages such as easy speed control, low maintenance, and regenerative capability. Brushless Permanent Magnet DC (BLDC) machines are also used in electric vehicles.
Stored energy in a battery is converted with a DC to AC converter to drive an electric vehicle. Battery technologies used in electric vehicles also developing in such a way that to store more energy. Other developments are – high energy density, charging speed, etc.
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Electric vehicle motors propel the vehicle converting electric energy to mechanical energy. Advancements of power electronics controllers made use of induction and synchronous motors in EVs easier.